Arc furnace roof



K. LEITNER ARC FURNACE RooF Filed March 30, 1955 Nov. 26, 1957 INVENTOR igr/ eafzer ATTORNEYS United Sttes Patent O ARC FURNACE ROOF Karl Leitner, Radenthein, Carinthia, Austria, assigner to General Refractories Company, Philadelphia, Ia.

Application March 30, 1955, Serial No. 498,004

4 Claims. (Cl. 263-46) Roofs composed in the preferred embodiment of magnesia or chrome-magnesia brick for electric arc melting furnaces were previously constructed by connecting to the outer reenforcement ring a ring of abutment brick, and connecting to the ring of abutment brick a corresponding number of rings of double conical brick, depending on the diameter of the roof, so as to extend to the center piece. In order to take into account the different diameters of the rings, these brick have necessarily had different dimensions. A large number of different brick-shapes have also been required for the center piece. Apart from the high cost of manufacture entailed by the numerous types of brick, this prior art roof construction has had the great disadvantage that no arrangement can be made for proper compensation for expansion and contraction in the roof, which occurs through variations in the temperature to which the roof is subjected.

There is a known method of compensating for excessive pressures which is applicable only at the time when the electric furnace roof of the character mentioned is iirst put into operation. This comprises inserting a compressible substance, such as asbestos, between the reenforcement ring and the abutment brick or inserting strips of paper, corrugated metal sheets, or the like in the joints between the brick. When, however, a roof of this type Cools, the materials provided to take up expansion do not resume their original shape, so that the roof subsides at the apex. When the roof is reheated, the apex rises again. This alternating action has the effect that the compressive forces between the brick act on the one hand on the inside edge and on the other hand on the outside edge of the brick and cause increased wear. This diculty is particularly critical when the centerpiece of the roof is partially worn. The centerpiece then usually collapses at a time when the thickness of the brick themselves is still suicient to permit further use of the roof.

. The disadvantages just described are also involved in the known electric furnace roofs in which the roof ring parts provided between the centerpiece and the ring of abutment brick consist of suspended ribbed brick and interposed panels of nonsuspended intermediate or grooved brick, after the manner of suspended ribbed arches having radial ribs. In this known type of electric furnace roof, since only the ribs are suspended, the centerpiece and the grooved panel must be replaced as a whole. The replacement of any particular part of the roof is not possible with this prior art construction.

The present invention contemplates providing an electric furnace roof which avoids the disadvantages above described. This permits laying of completely pressurefree brick with a few simplified brick-shapes, and also replacing of any roof brick without any danger of collapse of the other roof brick. According to this invention, the purpose is achieved by having all the roof brick lying between the abutment brick and the electrode mounts suspended on a carrying construction disposed above the roof. Stated in other words, the electric furnace roof of the present invention has all of the brick 2,814,476 Patented Nov. 26, 1957 ice suspended in the part of the roof which extends from the abutment brick at least to the centerpiece and which in consequence of the suspended brick imparts secure support to the centerpiece even when the centerpiece is directly composed of the electrode mounts.

It is, however, preferable to dispose the electrode mounts at distances from one another, and also to suspend on the supporting structure all brick situated between the electrode mounts. The electrode mounts are preferably rectangular or square in plan, while the suspended brick, which are preferably of identical size and shape, are disposed in rows running parallel to two opposite sides of the plan shape of the electrode mounts. In order to fasten the electrode mounts securely, it is sufcient to provide only the brick of the mount which are situated on two opposite sides of the electrode mount with wedge surfaces on the outside by means of which these brick are supported on the suspended roof brick while the brick of the electrode mounts situated on the opposite sides are of wedge shaped construction in the radial joints. In this construction only a few brick-shapes are necessary to make the electrode mounts. In addition it is sufficient for the support of the electrode mounts to provide hanging brick with an oblique side surface only on two sides of an electrode panel.

The supporting structure for suspending the roof brick consists in the preferred embodiment of girders, part of which extend in the direction of the parallel longitudinal rows of brick and another part of which extend transversely thereto, the transverse girders being advantageously disposed in the middle part of the roof containing the electrode mounts.

With regard to the suspension of the brick on the supporting structure, this is preferably accomplished by means of hammer shaped hangers which engage by their hammer shape part in undercut cavities, which are preferably formed by pressed-in sheet metal strips. Bricks jacketed with sheet metal, well known in the art as steel clad brick, are preferably used for the suspended brick. This makes the construction of the furnace roof extremely simple, and also makes repairs simple, since it is not necessary to use mortar or joining material.

Using the electric furnace roof of the present invention, it is not possible to obtain such great compressive forces between the various brick as to damage the brick material. In particular, it is also possible to construct the electric furnace roof of the present invention in the form of a flat roof.

The electric furnace roof of the present invention is illustrated in the drawing in one suitable embodiment, namely as a flat roof.

Figure l shows the furnace roof in plan, with the supporting structure removed in the *upper half and with the supporting structure present in the lower half.

Figure 2 is a section on the line 2 2 of Figure 1.

Figure 3 is a section on the line 3-3 of Figure 1.

An outer abutment ring 1 has an inwardly directed flange 2 on which the abutment brick 3 are supported. The remaining joints between the abutment brick 3 and the abutment ring 1 are lled with refractory joining material 4 for instance refractory mortar. The electrode apertures 5 are formed by electrode mounts which, as shown in Figure 1, have a rectangular or square plan.

Each electrode mount is formed by a plurality of bricks, which in the embodiment illustrated are 10, 11 20, 21 inclusive, of which the bricks 11, 12, 13 and 14 and 17, 18, 19 and 20 are situated on two opposite sides of the rectangle or square plan form and have wedge surfaces 23, 24 (Figure 3) on the outside, while the radial joints running between the brick pairs 10, 11; 14, 15; 16, 17; and 20, 21 are of wedge-shape so that the brick 10, 15, 16, and 21 have a genuine wedge-shape, while the brick 11, 14, 17 and 20 on the other hand have a reversed wedge-shape on the radial joints. This latter feature, however, is not detrimental to the support of the electrode mounts because the brick having a reversed wedgev shape are supported by the wedge surfaces 23, 24 on sus-v pended brick 25 as later described.

The roof parts situated between the abutment brick 3 and the brick -21 of the electrode mount on the one hand, and between the electrode mounts -on the -other hand are formed by brick 25 all of which are suspended. The brick 25 are identical in shape and size to one another, and, as shown particularly in the upper half of Figure 1, are disposed in parallel rows, only the hanging brick 25 adjoining the wedge surfaces 23-24 of the mount bricks having an oblique side surface adapted to these wedge surfaces, but in their other dimensions the hanging brick 2S are of identical construction to the other hanging brick 25.

The brick 25', 25, can be suspended singly or in groups. In the exemplied embodiment illustrated, the brick are suspended in pairs. The brick have for this purpose on their cold end opposite undercut suspension pockets 26, which are formed by pressed in Sheet metal strips 27. The hammer shaped parts of the hangers 28, which are suspended by their hook-shaped ends 29 on a supporting structure, engage in these pockets.

The supporting structure consists of longitudinal girders 31 to 39 and of transverse girders 40 to 46 which are extended in the manner illustrated in Figure 1 and joined together to form a supporting system in such a manner that each pair of brick 25 can be suspended by hangers 28 on the girder of the supporting structure situated thereabove. As shown in Figure 1, the transversely disposed girders are situated particularly in the region of the middle part of the roof containing the electrode mounts. Only the two transverse girders 40 and 46 extend radially outward to the surrounding ring 1. The supporting structure is of course provided in an opposite counterpart relation to the half shown, on the other half of Figure 1, and has been omitted in the upper half of Figure l merely to facilitate showing the brick construction.

The brick of the electric furnace roof of the present invention preferably consist of magnesite or chromemagnesite, Vand the suspended brick 25 and 25 preferably have steel clad side surfaces as shown for example in numerous U. S. patents of Russell Pearce Heuer, of which Heuer 2,155,165 granted April 18, 1939, for Furnace Roof, and 2,304,170 granted December 8, 1942, for Furnace Roof are examples.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims. Y

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A basic refractory brick roof for an electric arc melting furnace, including abutment brick and electrode mounts having generally rectangular plan shape, having a supporting structure above the roof and basic roof brick lying between the abutment brick and the electrode mounts suspended on the supporting structure, the suspended brick being disposed in rows running parallel to the respective sides of this plan shape.

2. basic refractory brick `roof for an electric arc melting furnace, including abutment brick and electrode mounts, having a supporting structure above the roof and basic roof brick lying between the abutment brick and the electrode mounts suspended on the supporting structure, the brick of the electrode mounts on the rst two opposite sides of the electrode mounts having wedge surfaces on the outer sides and being supported by these surfaces on hanging brick, the brick of the electrode mounts situated on the other two opposite sides of the electrode mounts being wedge-shaped in the radial joints and engaging reverse wedge faces of the brick on the rst two opposite sides.

3. A basic refractory brick roof for an electric arc melting furnace having brick in parallel brick rows, including abutment brick and electrode mounts, having a supporting structure above the roof which consists of girders, some of which extend in the direction of the parallel brick rows and others of which extend transversely thereof, and a basic roof brick lying between the abutment brick and the electrode mounts suspended on the supporting structure.

4. A basic refractory brick roof for an electric arc melting furnace having brick in parallel brick rows, including abutment brick and electrode mounts, having a supporting structure above the roof consisting of girders, some of which extend in the direction of the parallel brick rows and others of which extend transversely thereof, the girders running transversely to the parallel rows of brick being disposed in the middle part of the roof containing an electrode mount, and a basic roof brick lying between the abutment brick and the electrode mounts suspended on the supporting structure.

References Cited in the le of this patent UNITED STATES PATENTS 1,274,034 Grin July 30, 1918 1,329,891 Fitts Feb. 3, 1920 1,442,105 Stoop Ian. 16, 1923 2,021,424 McPherson Nov. 19, 1935 2,029,492 Lindner Feb. 4, 1936 2,155,165 Heuer Apr. 18, 1939 2,216,813 Goldschmidt Oct. 8, 1940 2,304,170 Heuer Dec. 8, 1942 

